The objective was to investigate the frequency and characteristics of tuberculosis (TB) in patients with systemic lupus erythematosus (SLE). We reviewed the charts of 556 patients with SLE who were followed up between 1978 and 2001 in our lupus clinic. Patients who developed TB after the diagnosis of SLE were identified (SLE/TB+). Ninety-six consecutive patients with SLE who did not develop TB during the follow-up were evaluated as a control group (SLE/TB-). Clinical, laboratory and management characteristics of these two groups of patients were recorded according to a predefined protocol, and compared. Of the 556 patients evaluated, 20 patients (3.6%) with TB were identified. Nine of the 20 patients (45%) had extrapulmonary TB (vertebral involvement in three patients, meningeal in two, and joint and soft tissue in four). Arthritis and renal involvement were significantly high in the SLE/TB+ group (P = 0.045, P = 0.009, respectively). The mean daily dose of prednisolone before the diagnosis of TB and the cumulative dose of prednisolone were significantly higher in the SLE/TB+ group compared to the SLE/TB- group (27 +/- 22 g versus 16 +/- 16 g, 24 +/- 45 mg versus 11 +/- 8.5 mg, respectively). In conclusion, we found an increased frequency of TB infection and a high prevalence of extrapulmonary TB in a large cohort of SLE patients. The mean daily dose of prednisolone before the diagnosis of TB and the cumulative dose of prednisolone, which possibly related to disease severity, were important determinants for the increased risk of TB in these patients with SLE.